JPH05296309A - Ball screw for semiconductor manufacturing equipment - Google Patents

Abstract

PURPOSE:To provide a ball screw for semiconductor manufacturing equipment, with a lubrication film having nonconductivity, low dust generation property, high lubrication performance, high durability, and high corrosion resistant property. CONSTITUTION:A device is provided with a screw shaft 1 formed, in its outer peripheral surface, with a helical inside track surface 1a, a ball nut 2 formed, in its inner peripheral surface, with a helical outside track surface 2a, and a plurality of balls 3 disposed in a helical space formed between the inside and the outside track surfaces 1a, 2a. A lubricating film made of fluoropolyether polymer or polyfluoroalkyl polymer having functional groups such as epoxy groups, isocyanate groups, is formed on respective tip portions of balls 3, circulation groove 6a, and deflector 5 of a ball screw composed of a deflector 5 and a guide plate 6 serving as circulation members.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ball screw used in a semiconductor manufacturing facility.

[0002]

2. Description of the Related Art A ball screw has a plurality of balls arranged in a spiral ball circulation path formed between a screw shaft and a ball nut inserted through the screw shaft, and the screw shaft is circulated by rolling the balls. Power is transmitted between the ball nut and the ball nut, but the ball rolls while slipping under the combined force of the rotational and axial directions, so at the contact area between the ball and the ball circulation path. Rolling friction and sliding friction occur simultaneously. Further, when the balls collide with each other, the rotation directions of the adjacent balls are reversed, so that the relative sliding speed between the balls is double that of a single ball, and a large frictional force is generated. For these reasons, the selection of lubricant is particularly important for ball screws.

Usually, a fluid lubricant such as grease is used as a lubricant for the ball screw, but when it is used in a sealed vacuum that requires high cleanliness such as in semiconductor manufacturing equipment, the lubricant is It is not possible to use a fluid lubricant such as grease because steam becomes a pollution source of the environment. for that reason,
In such an environment, a solid lubricant is generally used. Currently, as solid lubricants, layered substances such as molybdenum disulfide, soft metals such as gold, silver and lead, polymers such as PTFE and polyimide, and composite materials thereof are widely used. ..

[0004]

In recent years, in the field of semiconductor manufacturing, the line width of conductive patterns has become finer as the degree of integration of semiconductors has increased. As a result, the adherence of particles onto conductive patterns is extremely avoided. Tend to do. Unlike the fluid lubricant, the solid lubricant does not have a risk of contaminating the environment by evaporation, but it is necessary to consider dust generation during the wear and transfer process of the lubricating film. In particular, with respect to the ball screw, the threaded portion is exposed, and it is difficult to suppress dust generation by a seal or the like like a bearing, so countermeasures against dust generation are also an important issue. For example, in a soft metal-based solid lubricant, the wear powder itself has conductivity, and therefore if the wear powder adheres to the conductive pattern, the conductive pattern may be short-circuited. Solid lubricants based on layered materials such as molybdenum disulfide are
It is not conductive, but has poor wear resistance and a large amount of dust. In addition, polymer type solid lubricants such as PTFE are inferior to soft metals in terms of wear resistance and durability and generate a large amount of dust.

Further, recent semiconductor manufacturing facilities are required not only to be used in a vacuum but also to have functions of dual use in the atmosphere and vacuum, corrosion resistance, heat resistance and the like. That is, the ball screw is mainly used in the semiconductor manufacturing equipment in the wafer processing process. The apparatus used in this step tends to be in-line for improving productivity, and a wafer transfer apparatus is required to have a ball screw which can be operated in both atmosphere and vacuum environment. Further, corrosion resistance and heat resistance are also required depending on the place of use.

In view of the above, the present invention solves the above-mentioned problems and provides a lubricating coating for a ball screw with characteristics such as non-conductivity, low dust generation, high lubricity, high durability and high corrosion resistance. In addition, these characteristics are
An object is to make a ball screw suitable for semiconductor manufacturing equipment so that it can be exhibited in both vacuum environments.

[0007]

In order to solve the above problems, in the present invention, a screw shaft having a spiral inner raceway surface formed on the outer peripheral surface and a spiral outer raceway surface formed on the inner peripheral surface. A ball nut, a plurality of balls arranged in a spiral space formed between the inner and outer raceways, and a circulation member that connects the spiral spaces to form a series of ball circulation paths. In the metal ball screw having, the fluorine-containing heavy metal having a functional group having a high affinity for these metal materials on at least the surface of the ball among the surface of the ball and the surface of each member constituting the ball circulation path. That is, a structure in which a lubricating coating made of coalescence is formed is adopted.

[0008]

The ball screw for semiconductor manufacturing equipment according to the present invention has a coating film made of a fluorine-containing polymer formed on at least the surface of the ball screw, and further on the surface of each metal member constituting the ball circulation path, with respect to the metal. Since it has a functional group with high affinity and has high adhesion to the surface of each member, abrasion powder is less likely to scatter and dust generation is further reduced. In addition, the functional group protects each member and improves corrosion resistance. Furthermore,
Due to the original properties of the fluoropolymer, the friction coefficient is low, the heat resistance is excellent, and the lubricating coating having good lubricating performance is maintained for a long period of time.

[0009]

EXAMPLES The fluorine-containing polymer in the present invention is a polyfluoroalkyl polymer, a fluoropolyether polymer or the like. And, as the polyfluoroalkyl polymer, for example, those shown in the following chemical formula 1 can be mentioned,
The fluoropolyether polymer, -C _x F _2x -O-
A unit represented by the general formula (X is an integer of 1 to 4) is a main structural unit, and each has a number average molecular weight of 1000 to 5
It is a polymer of 0000.

[0010]

[Chemical 1]

The functional groups having a high affinity for metal ball screw materials include epoxy groups, amino groups, carboxyl groups, hydroxyl groups, mercapto groups, isocyanate groups,
Examples thereof include sulfone groups and ester groups, and specific examples thereof include those represented by the following chemical formulas 2 and 3.

[0012]

[Chemical 2]

[0013]

[Chemical 3]

Such a fluorinated polymer may be used alone or in combination of two or more kinds. In that case, it is desirable to take care so that the combined groups react with each other to make the polymer have a higher molecular weight and obtain a film having more excellent abrasion resistance.

The method for applying the above-mentioned fluoropolymer is as follows:
An ordinary coating method may be used, and although not particularly limited, for example, the fluoropolymer may be dissolved in a suitable solvent and applied (including spraying, dipping, etc.), and then the solvent may be evaporated. Alternatively, a method of heating after forming a thin film to increase the molecular weight of the film-forming component or baking may be employed.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment in which the present invention is applied to a guide plate type ball screw. This ball screw includes a screw shaft 1 having a spiral inner raceway surface 1a formed on an outer peripheral surface,
A ball nut 2 having a spiral outer raceway surface 2a formed on the inner peripheral surface thereof, a plurality of balls 3 arranged in a spiral space formed between the inner and outer raceway surfaces 1a, 2a, and a spiral space Is formed by a deflector 5 and a guide plate 6 as a circulation member that connects the above-mentioned components to form a series of ball circulation paths.
The ball 3 rolling between the screw shaft 1 and the ball nut 2 is scooped up by the deflector 5 provided on the inner surface of the ball nut 2, and is screwed again through the circulation groove 6a of the guide plate 6 attached to the ball nut 2. It circulates back to the space between the shaft 1 and the ball nut 2.

The ball 3 of this ball screw, the surface of the circulation groove 6a shown in FIG. 2 and the tip portion (tongue portion) 5a of the deflector 5 shown in FIG.
In addition, 3a in FIG.1 (c) shows a lubrication film.

That is, an isocyanate group-containing perfluoropolyether polymer (number average molecular weight of 2000) represented by the following chemical formula 4 is diluted with an organic solvent, and the whole or a substantial part of the above-mentioned three constituent parts is added thereto. Soaked. This was taken out and heated at 150 ° C. for 30 minutes to form a lubricating film, which was then attached to a ball screw.

[0019]

[Chemical 4]

The rotation speed of the obtained ball screw was 40
0 rpm, preload amount 15 kgf, vacuum degree 10 ^-7 Torr level,
The ball screw was operated under the condition of room temperature to carry out a life test and a dusting test, and the results are shown in Table 1.

A ball screw separately manufactured under the same conditions as above was allowed to stand in an atmosphere of 50 ± ° C. and 95% RH or more, and the time until rusting was examined. The results are also shown in Table 1. ..

[0022]

[Table 1]

[Comparative Example] A ball screw assembled in exactly the same manner except that a silver lubricating coating was formed by plating instead of the fluorine-containing polymer, under the same conditions as those in the working example. A rust test was conducted, and the results are also shown in Table 1.

As is clear from the results of Table 1, in the examples of the present invention, the relative life was more than twice, the relative dust generation amount was one-fifth or less, and the relative rusting time was five times in comparison with the comparative examples. As described above, it showed extremely good durability, low dust generation and corrosion resistance.

Although the guide plate type ball screw has been described in the above embodiment, a so-called return tube type ball screw, a coma type ball screw and others are also provided with a lubricating coating on at least the ball surface. Of course, it can be carried out in the same manner.

[0026]

As described above, according to the present invention, the surface of the ball screw and further the surface of each member constituting the ball circulation path are coated with a lubricating film made of a fluoropolymer having excellent adhesiveness. It is said that it is the most suitable as a ball screw for semiconductor manufacturing equipment, because it has the characteristics required in 1. That is, it is non-conductive and has low dust generation, high lubricity, high durability and high corrosion resistance. be able to.

[Brief description of drawings]

FIG. 1 (a) is a perspective view showing an embodiment, and FIG. 1 (b) is (a).
A-A line sectional view, (c) is a sectional view of the ball

FIG. 2 is a perspective view showing a guide plate of the embodiment.

FIG. 3 is a perspective view showing a deflector of an embodiment.

[Explanation of symbols]

 1 screw shaft 1a inner raceway surface 2 ball nut 2a outer raceway surface 3 ball

Claims (1)

[Claims] 1. A screw shaft having a spiral inner raceway surface formed on an outer peripheral surface, a ball nut having a spiral outer raceway surface formed on an inner peripheral surface, and a spiral formed between the inner and outer raceway surfaces. In a metal ball screw having a plurality of balls arranged in a space and a circulating member that connects the spiral space to form a series of ball circulation paths, the surface of the ball and the ball circulation path are A semiconductor manufacturing facility characterized in that a lubricating film made of a fluoropolymer having a functional group having a high affinity for these metal materials is formed on at least the surface of the ball among the surfaces of the constituent members. Ball screw.